Density-driven spontaneous streak segregation patterns in a thin rotating drum

Abstract

Granular mixtures may segregate because of external driving forces, which play an important role in industry and geophysics. We investigate experimentally the mechanism of density-driven spontaneous streak segregation patterns in a thin rotating drum. We find that a spontaneous streak segregation pattern can occur in such a system, which we call a D-system. A phase diagram identifies three segregation pattern regimes in this study: the mixing regime, the core segregation regime, and the streak segregation regime.

Effects of density ratio, rotation speed, and fill level on density-induced granular streak segregation in a rotating drum

“…3(c)-(f)). In core segregation cases, heavy particles sink to the lower part of the flowing layer and have lower velocities than light particles do [1,20]. However, heavy particles have higher velocities than light particles do in granular streak segregation cases because a binary mixture exhibits larger differences in the repose angle and density ratio [20].…”

“…Axial motion may become significant as the axial thickness is increased. Hence, a dimensionless axial thickness of 3 was applied to balance the wall friction and axial motion according to previous studies [20]. Six density ratios were used to study the density-induced evolution and dynamic behavior of granular streak segregation.…”

“…Conversely, a thicker and slower flowing layer is formed from large particles. Liao et al [20] found that the dimensionless differences in the dynamic repose angle and density ratio strongly affected streak segregation patterns caused by the density. They provided a phase diagram in which three pattern regimes were identified: the core segregation regime, streak segregation regime, and mixing regime.…”

“…Rotating drums are widely used to investigate the flow mechanics and segregation mechanism of granular flows because the flow field in such drums is relatively simple [1,3,[6][7][8][9][10][12][13][14][15][16][17][18][19][20]. Granular flow in a rotating drum has different regimes depending on the Froude number.…”

Granular segregation in a thin drum rotating with periodic modulation

“…Radial segregation in thin rotating drums occurs, for example, when particles differ in density [9] or size. In the latter case, smaller particles group to form a central core, and larger ones accumulate in the outer wall region.…”